Decreases wear on gun
Breaks less balls
Increased cloud size from the end of the barrel (C02)
A very good product, definetly the most worthwhile upgrade to your Piranha, second only to a new barrel. The increase C02 cloud is noticably bigger on my setup, especially on hot days. With the bolt installed my marker lost the metal 'ching' sound when it fired, making a pretty quiet gun much quieter. I also find with the bolt I can use cheap paint (Rec Sport) without fear of breaking a ball like I did with the stock bolt.
I bought this accessory halfway through the 4th year that I owned my marker, and it has made a huge difference. After being able to use it for a few games last year and one so far this year (stopped for winter, no indoor places around here) I can say that this product, though expensive, is a worthy addition to your gun.